Composite structures are desirable in many industries for many applications. For example, aircraft, space, and land/sea vehicles employ a variety of curved and multiple-contoured surface structures in their fabrication. Composite materials are commonly used for these structures because, among other desirable attributes, composite materials have high strength-to-weight ratios and allow the design and fabrication of large integrated composite structures. Even so, structures formed from composite materials oftentimes need to be stiffened or joined to adjacent structures. Therefore, manufacturers of composite structures are continually searching for better and more economical ways of stiffening and/or assembling composite structures.